SOUTH PORTLAND — Marijuana advocates turned in 1,521 petition signatures seeking a legalization referendum in South Portland on Monday, marking a key milestone in what may be the Maine effort’s toughest battle yet.

While the Marijuana Policy Project and its coalition of supporters faced little in the way of outspoken resistance while campaigning for a legalization ordinance in Portland last fall, many city officials in neighboring South Portland have asserted staunch opposition to the measure.

After their success at the polls in Maine’s largest city — where two-thirds of the voters who cast ballots in November approved of legalization — marijuana advocates have launched summer petition drives in York, Lewiston and South Portland.

The Marijuana Policy Project and its backers have turned in signatures in York, where a public hearing will take place on July 28 before selectmen there consider placing legalization on the November ballot, and South Portland.

The 1,521 names collected by petitioners in South Portland must be certified by the city clerk’s office during the next 20 days. The petitioners will need 959 to be certified as registered South Portland voters in order to force a referendum vote on the matter.

David Boyer, Maine political director for the Marijuana Policy Project, told reporters during a news conference on Monday that his group has gathered about half of the 859 signatures necessary in Lewiston, and petitioners there have until early August to finish gathering signatures.

Like during the Portland campaign, Boyer on Monday compared recreational use of marijuana to that of alcohol, saying the drug is safer to use and therefore should be legal — and similarly taxed and regulated.

“We don’t punish adults for drinking wine in their homes,” Boyer said. “That would be silly. We think it’s just as illogical to punish adults for using small amounts of marijuana in their homes.”

Unlike in Portland, where the legalization ordinance allows for possession of 2.5 ounces of marijuana under local law, the proposed ordinances in South Portland, York and Lewiston would permit possession of just 1 ounce. Boyer reiterated on Monday that his group is seeking the municipal-level legalization measures as a precursor to a 2016 effort to legalize recreational marijuana use statewide.

As is the case in Portland, the marijuana ordinances petitioners are proposing in the other three communities would apply to adults over the age of 21 and would maintain prohibitions on public use or display of the drug.

Portland police and state prosecutors have maintained that, despite the local ordinance legalizing pot in the city, they are still obligated to enforce state and federal laws outlawing the drug, leaving the referendum vote there largely as a ceremonial or advisory one.

But in that same vein, Boyer said Monday that “by South Portland voters passing this, the town will be sending a message to the state,” adding to the growing collective of voices seeking a larger scale legalization.

“This is the happiest revolution you’ll see,” said legalization supporter and signature gatherer Melissa Thomas at Monday’s news conference. She also drew a comparison between marijuana and alcohol.

“We’re not going to give our kids margaritas or daiquiris, and we’re not going to feed our kids herb,” she said.

Joining the voices in South Portland was Democratic U.S. Senate hopeful and former American Civil Liberties Union of Maine leader Shenna Bellows, who described herself as the country’s first Senate candidate to openly endorse marijuana legalization.

Bellows, who is challenging incumbent Republican Susan Collins for the seat, pledged to fight for legalization on a federal scale if elected. She also called for criminal justice reform, announcing her support of a bill by U.S. Sens. Rand Paul, R-Kentucky, and Cory Booker, D-New Jersey, that would expunge the nonviolent criminal records of juveniles, among other measures.

“It’s time to end the failed war on drugs and take a new approach,” she said.

But while opposition to the legalization effort across the bridge in Portland was largely muted, resistance in South Portland has already been prominent.

Last month, the South Portland City Council unanimously passed a nonbinding resolution opposing legalization. That action came on the heels of a news conference at which Mayor Jerry Jalbert, Police Chief Ed Googins, Superintendent Suzanne Godin and two city councilors — among others — proclaimed their opposition.

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